Epidemiologic studies are conducted to identify and quantify occupational and other causes of cancer and to understand mechanisms of carcinogenesis. Major etiologic investigations focus on working populations exposed to benzene, other organic solvents, aromatic amines, acrylonitrile; formaldehyde, diesel exhausts, and silica. Case-control studies of non-Hodgkin's lymphoma, multiple myeloma, leukemia, mesothelioma and cancers of the lung, brain, bladder, stomach, liver, prostate, pancreas and head and neck evaluate risks from occupational and lifestyle factors. Etiologic investigations of occupation utilize modern methods to assess occupational exposures and to integrate biochemical components to elucidate mechanisms of carcinogenic action and individual susceptibility. Major new efforts currently underway focus on workers exposed to benzene, miners exposed to diesel exhausts, aircraft mechanics exposed to trichloroethylene and other solvents, and workers producing and using acrylonitrile. Extended mortality follow-up is underway for previously completed cohort studies of workers exposed to formaldehyde, perchloroethylene, trichloroethylene, and other organic solvents. Recent findings include evidence of a dose-response relationship of benzene exposure with mortality from leukemia and non-Hodgkin's lymphoma. The dose-response results are supported by parallel investigations showing that benzene-related hepatotoxicity tracks with historical benzene exposure estimates. Brain cancer excesses were found among grain farmers, rubber and transportation equipment workers in a case-control investigation among women in Shanghai, China. Another case-control study showed stronger associations of asbestos with pleural mesothelioma among men with a family history of cancer than without, although no statistical evidence of an interaction was detected. A comprehensive report linking occupation and cause of death for 1.7 million deaths in 23 states provides leads for further analytic studies. In other reports, exposures to dust and benzo(a)pyrene were linked to excesses of lung and stomach cancer among iron and steel workers, silicosis was linked to lung cancer, textile work was linked to biliary tract cancer, and female electrical workers did not show excess breast cancer mortality.